Montana Field Guide

The following is taken from Vickery and Kevan (1985), Phadt (2002), Capinera et al. (2004), and Scott (2010). This is a medium-sized grasshopper. The body length to end of forewings is 16-20 mm for males, and females 19-25 mm. Usually greenish but can vary from tan or grayish. A dark stripe occurs on the dorsal surface of the head and extends onto the pronotum. A dark stripe crosses the lateral lobe of the pronotum. The forewings are pale green or brown and can be shorter or longer than the abdomen. The hind femur has 3 dark stripes, and the tibia is bluish or bluish-green. The tip of the abdomen bears a small protuberance.

The Thistle Grasshopper passes the winter in the egg stage and is an early hatching species. The first instar nymphs begin appearing late April or the first of May. Adults occur into October, depending upon temperatures and other weather factors (Vickery and Kevan 1985, Phadt 2002, Capinera et al. 2004).

The following is taken from Vickery and Kevan (1985), Phadt (2002), Capinera et al. (2004), and Scott (2010). Most useful characteristics are: 1) Shape of the pronotal disk, which widens progressively from front to rear. 2) A triangular pointed cercus of the male’s genitalia. 3) Pointed ventral spine between front legs. 4) Three dark markings on the upper medial area of the femur. 5) Hind tibia medium blue with a pale tan ring at the base.

The Thistle Grasshopper can be confused with species in the genus Melanoplus. It is distinguished by the shape of the spine protruding ventrally between the front legs. The spine is more slender and sharply pointed in this species than in the Melanoplus (Capinera et al. 2004).

Thistle Grasshoppers inhabit desert shrub, alkali flats with saltbush and black greasewood (Sarcobatus vermiculatus), and grasslands. Their habitats are usually on disturbed land, crop borders, and weedy rangelands (Capinera et al. 1982 and 2004, Pfadt 2002).

This species feeds primarily on forbs and some woody shrubs of the Chenopodiaceae such as: Russian thistle (Salsola tragus), common kochia (Kochia scoparia), white goosefoot (Chenopodium album), and saltbush sp. It does not feed on grasses. There have been reports of this species reaching high population densities (outbreaks) and damaging sugarbeet crops. Overall, this species in considered beneficial in suppressing weedy species (Capinera et al. 1982 and 2004, Pfadt 2002).

The following is taken from Capinera et al. (1982, 2004) and Pfadt (2002). Observations indicate that eggs are laid on bare ground in pods, consisting of 12 to 18 eggs. This species’ fecundity is high. One lab study of six caged females produced an average of 250 eggs each. Upon hatching, the nymphs grow through 5 nymphal instars and have a relatively long development period to the adult stage ranging from 50 to 60 days.